Hitherto in the art of ink-jet printing, a common technique for feeding paper or other media to a print-head head has involved the use of pick-off or feed rollers which are specifically dedicated to the transferring of paper from a paper tray to the area of the printer between the printhead and the paper support member (platen) adjacent thereto. In this latter area, there is required an additional paper drive mechanism used to continue the transport of the paper past the printhead and printing zone and onto a paper collection tray or the like. Indeed, often a third drive is used with respect to transporting the paper to the paper collection tray.
Thus, the printer drive assembly requires a first drive mechanism for transporting paper out of the paper supply tray and a second paper drive mechanism for transporting paper past the printhead and into the paper collection tray. The requirement of multiple paper drive mechanisms adds to the cost and complexity of the ink-jet printer.
In addition, such prior ink-jet printers must deal with the problem of ink drying, unless specially coated paper is employed. If no mechanism is provided for drying the ink, then, with the rapid output of paper, one sheet is placed in the paper output tray before the ink on the sheet underneath has had an opportunity to dry, thereby causing smearing of the print on the lower sheet. One common mechanism is to provide some sort of drying means, such as a lamp or heater. However, such a requirement also adds to the complexity of the printer, since a power source, lamp or other heating device, and associated apparatus must be provided. Such apparatus also adds to the weight of the ink-jet printer.
It is thus desired to reduce the cost and complexity of the printer, while simplifying the components and their interactive association. It is also desired to provide means for handling printed media in a manner that prevents smearing of previously-printed sheets of the print medium.
Ink-jet printers comprise a plurality of interrelated components for printing on a print medium, such as paper. For example, the print zone of the paper is supported on a platen, and a print cartridge, secured in a bidirectionally movable carriage, prints characters on the paper in the print zone through a printhead in the cartridge.
There are several aspects of the printing that must be controlled to achieve consistency in printing from one sheet to the next and from one sheet thickness to another. For example, the printhead-to-paper space must be controlled, as must the printhead-to-paper angle.
The carriage moves on a shaft substantially parallel to the print zone, and the degree of parallelism must be controlled in order to assure uniformity of print across the sheet of paper. Further, the print medium is moved through the print zone by means of a drive roller mounted on a drive shaft. This drive shaft should also be maintained parallel to the print zone. Finally, the printer must be able to maintain the paper flat against the platen and deal with cockling of the paper, which occurs due to the presence of wet ink. Cockling tends to cause the gap between the paper and the printhead to vary.
In ink-jet printing technology, a printhead, comprising a plurality of nozzles in a nozzle plate, is fluidically associated with a reservoir of ink. The printhead is mounted on one end of a print cartridge and the reservoir is provided inside the cartridge.
An interconnect means is provided, which carries electrical signals from a microprocessor in the printer to the printhead. For thermal ink-jet printers, these signals provide a current to resistors associated with the nozzles and thus control the heating of specific resistors, which in turn form droplets of ink. The droplets of ink are expelled through the nozzles toward a print medium, such as paper. The particular pattern of resistor heating controls the pattern of characters formed on the print medium.
The print cartridge is supported in a carriage, which is adapted to move bidirectionally, perpendicular to the movement of the print medium through the printer. The carriage movement is controlled by a motor and an associated belt drive, with the motor controlled by the microprocessor.
Insertion of an ink-jet cartridge into the carriage often necessitates use of two hands. Further, many cartridge/carriage configurations do not provide simultaneous alignment of the nozzle plate in the X, Y, and Z directions. Finally, contact between the printhead and the interconnect means must be reliably made, in order to ensure proper nozzle firing.
Accordingly, it is desired to provide a cartridge/carriage assembly that includes the foregoing advantages without the limitations of the prior art.
Service stations in ink-jet printers are intended to maintain a thermal ink-jet printhead in good working order for the service life of the printhead. As is well-known to those skilled in this art, the printhead is formed as part of a printing cartridge. The cartridge contains a reservoir of ink, and the printhead contains an assembly of passageways, firing elements (resistors) and nozzles for firing droplets of ink toward a printing medium, such as paper.
During the course of operation, it is possible for nozzles to become clogged with ink and for bubbles of air to be trapped in such a manner as to interfere with the correct operation of the printhead. Also, it is desired to prevent contaminants, such as paper dust, from affecting the operation of the nozzles and to prevent ink from drying in the nozzles when the printhead is at rest. Finally, it is desired to clear out soft viscous plugs of ink, which may form while the printhead is at rest. This should be done prior to initiation of printing, to ensure that all nozzles in the orifice plate of the printhead are firing properly.
A service station can address the afore-mentioned problems and requirements. While service stations are not per se novel in thermal ink-jet printing, it is a goal to provide a service station with easy operation which maximizes a number of functions in a minimum of space. The preferred service station has a number of functions, including:
1. clear clogged nozzles and remove bubbles; PA1 2. cover nozzles when the printhead is not in use to prevent contamination thereof; PA1 3. prevent ink from drying out in the nozzles when the printhead is not in use; PA1 4. wipe contaminants picked up during printing off of nozzles; and PA1 5. provide a location to fire nozzles into for clearing out the soft viscous plugs of ink. PA1 (a) a paper supply means for providing a supply of a medium to be printed; PA1 (b) a paper collection means for collecting printed medium; PA1 (c) means for conveying a sheet of the medium from the paper supply means to the paper collection means through a printing zone; PA1 (d) a cartridge provided with a printhead and mounted on a carriage cooperatively associated with a carriage guide and adapted to move orthogonal to movement of the medium supported on a platen maintained in the printing zone; PA1 (e) means for creating a reverse bow in the sheet of the medium for directing the sheet in a plane parallel to the printing zone just prior to entering the printing zone for maintaining flatness of the sheet; PA1 (f) means for referencing the carriage and the print medium to the carriage guide; PA1 (g) means for permitting ink on a previously-printed sheet of the medium to dry during printing of the next sheet of the medium and for conveying the printed sheet to the paper collection means; and PA1 (h) means for controlling the medium-conveying and the printing operations. PA1 (i) means for moving the member from an initial closed, sheet-supporting position to an open position, wherein the sheet is no longer supported; and PA1 (ii) means for returning the member to the initial position. PA1 (a) means for priming the printhead, PA1 (b) means for actuating the service station by the carriage; PA1 (c) means for sealing the printhead during non-printing operations, and PA1 (d) means for cleaning the printhead.